Actuating means for a motor vehicle locking brake

ABSTRACT

An actuating device for a locking brake of a motor vehicle includes a reversible electric motor which drives a threaded spindle with a serrated coarse screw thread through a preferably self-locking gear connection. A spur lever having a spur which engages the screw thread is connected to a force-transmitting member which actuates the tensioning element of the locking brake. The electric motor and threaded spindle turn in one direction to set the locking brake and in the opposite direction to release the locking brake. The actuating device also includes a manually operated handbrake lever which can pivot about an axis spaced from and transverse to the longitudinal direction of the spur lever and the force-transmitting member. When the handbrake lever is pulled, an actuating lever pivotally mounted on the same axis causes the spur lever to pivot toward the brake-locking position.

BACKGROUND OF THE INVENTION

The invention relates to an actuating means for a motor vehicle lockingbrake.

A locking brake of this kind is disclosed in principle by German Lettersof Disclosure 2,035,349. This known locking brake is intended to becapable of automatic engagement and disengagement in any operating modeof the vehicle, such as for example starting, setting in motion,changing gears, clutch action, standing and parking. However, noconcrete design or control features are disclosed in that source. It ismerely set forth schematically and implicitly that in the train ofelectrical supply to an electric motor, several electric switches are tobe arranged, associated with the ignition, clutch and transmission ofthe motor vehicle, their conditions depending on the current functionalmode ignition on/ignition off, clutch in/clutch out, andin-gear/neutral, while an additional electric switch, apparentlymanually actuable, can render the aforementioned electric switchesinoperative and control the electric motor directly.

SUMMARY OF THE INVENTION

The object of the invention, then, is to create an actuating means thatmeets the requirements of practice as to mode of operation anddependability in service, and furthermore affords numerous additionalpossibilities for control and functional monitoring of the lockingbrake.

This object is accomplished, according to the invention, by providing abrake actuator having a threaded spindle driven by a reversible electricmotor and a brake-actuating lever connected to the brake and having aspur gear engaging the spindle thread, the mechanical linkage betweenthe motor and the lever including a self-locking connection.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing, in part schematically and in principle,

FIG. 1 shows a view of an actuating means according to the invention;and

FIG. 2 shows a detail of said actuating means;

FIG. 3 is an enlarged fragmentary side view illustrating the brakeactuator portion of FIG. 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The drawing shows only those details of the actuating means which arenecessary for an understanding of the invention.

The actuating means represented by way of example is an apparatus thatmay be operated purely mechanically in the manner of known hand brakemechanisms, or purely electrically, with no need to execute anyswitching maneuvers or the like. The apparatus comprises an electricmotor 1 driving a threaded spindle 4 whose coarse thread 5 is preferablyof serrated configuration.

The thread 5 is engaged by the spur 6 of a lever 7 urged towards thespindle 4 by spring arrangements 13, as clearly indicated in FIG. 2. Thelever 7 in turn is articulated to the motor end of the transmissionelement 2, in communication with the locking members of the lockingbrake, not explicitly shown, of the motor vehicle. The transmissionelement preferably used, as in the embodiment shown by way of example,is a cable in the nature of a Bowden release, whose cable 21 isconnected to the lever 7, while its sleeve 22 abuts in conventionallyfixed location on the vehicle framework, not shown in detail.

The electric motor 1 used is preferably a known direct-current motorsupplied from a battery carried on the vehicle and capable of beingswitched on and off or in direction of rotation according to prevailingrequirements by means of an electric switch 1a and/or an electronicregulating and control means 1b, not shown in detail. Preferably anelectric reversing switch is used for this purpose.

For electrically setting and electrically releasing the locking brake,the electric motor 1 is switched in in each instance by actuating thereversing switch 1a, the direction of rotation of the electric motor andhence the direction of rotation of the threaded spindle 4 depending onthe direction of actuation of the switch 1a. According to the directionof rotation of the spindle 4, therefore, the lever 7, with its spur 6engaging the thread of the spindle and the cable 21 of the transmissionelement 2 acting thereon, is moved in either the one direction or theother axially. To actuate the locking brake, the reversing switch isoperated so that the lever 7 is moved out of its fully extended restposition "a" as shown in the direction of the arrow x, for example intoposition "b," whereby a tension tightening the locking members istransmitted to the locking members of the brake by the cable 21 of thetransmission element 2.

As soon as the locking brake has been set, or a desired locking force isattained, the electric motor 1 is shut off, either by releasing theaforesaid reversing switch 1a or else automatically by means of anelectronic regulator and control 1b, not shown in detail. The lockingforce of the brake is fully maintained even though the electric motor isswitched off, if the gear 3 and/or the thread 5, or the pair comprisingthread 5/spur 6, is of self-locking design; so no retaining forces needbe applied by the electric motor 1.

For electrically releasing the set locking brake, the electric motor isswitched on again by suitable switch actuation, but in the opposeddirection of rotation, so that the lever 7 is moved back again, into theposition marked "a" in FIG. 1 at the farthest. The transmission element2, or cable 21, after elimination of the tension exerted by the lever 7,is likewise retracted in turn to its original position by theconventional restoring springs or the like of the brake.

To switch the electric motor 1 on and off and at the same time determineits direction of rotation as required to set or release the lockingbrake, as the case may be, preferably a manually actuated electricreversing switch 1a is provided, as aforementioned.

Alternatively, however, an additional electronic regulating and controlmeans 1b may be provided, both to monitor proper function of theapparatus and to control the locking brake in dependency upon operatingparameters of the motor vehicle and/or of the electric motor 1.

Advantageously, the electric motor 1 may be switched off automatically,for example by such electronic regulating and control means 1b, when itsmotor current exceeds a predetermined value, or else when it has nolonger been rotated for a certain length of time. For this purpose, ofcourse, suitable known sensors 1c and 1d must be provided, to gaugefirstly the motor current and secondly the rotational speed of the motorshaft, the initial values whereof are supplied to the electronicregulating and control means 1b. By varying this motor current limit, itis thus possible in simple manner to adapt to special operatingconditions from time to time prevailing. For example with the aid of aninclinometer 1e or the like installed in the vehicle, it will thus bepossible to vary the said motor current limit as a function of the up ordown grade of the roadway, namely in such manner that the limit iscorrespondingly increased with the magnitude of the grade or inclinationof the roadway. Correspondingly to the increased motor current limit,the electric motor 1 will then be switched off only at a higher motorcurrent, or in other words not until a correspondingly higher lockingforce is made to act on the locking brake. The vehicle load or thetowing of a motor vehicle trailer may be taken into account in simplemanner by varying the motor current limit.

It is easily seen that in setting the locking brake, i.e. with lever 7moving in the direction of the arrow x, brake lining wear or variationsin cable length are automatically compensated without loss of brakeforce.

Conceivably also, the electric motor 1 may simply be switched off inresponse to axial force upon reaching the position "b" (locking brakeset) or that of the stop in position "a" (brake released) as representedin FIG. 1.

In the actuating means according to the invention, using the electronicregulating and control means 1b, the ability of the system to functionproperly may also be monitored continuously in very simple manner. Whenthe electronic regulating and control means 1b is notified, for exampleby signals from current and speed sensors 1c and 1d, that firstly themotor current is too high and secondly too few motor revolutions, or toofew spindle revolutions, are being executed, then the electronicregulating and control means 1b, with the aid of the logic components itcontains, for example microprocessors or the like, will conclude fromthese data that the locking brake is apparently jammed, for examplerusted or frozen.

Correspondingly, the electronic regulating and control means 1b, whenfirstly the motor current ceases to rise and secondly too many motor orspindle revolutions are detected, will diagnose in simple manner thatthe transmission element 2 has failed, or else, for example due to cablestretch, become too long. The electrically operated locking brakeactuation means according to the invention may also advantageously becoupled to a conventional theft alarm system, for example in such amanner that the locking brake will be automatically set when an alarmhas been triggered.

Using the electronic regulating and control means, it is possible alsoto achieve an "automatic actuation of locking brake when standing on aslope" function or an "automatic actuation of locking brake when vehiclestationary" function, for which purpose in principle it is necessaryonly with the aid of suitable sensor means to detect the standstill ofthe vehicle and--in the former case--the inclination of the roadway, andsupply the sensor signals to the automatic regulating and control means.Especially for motor vehicles with automatic transmission, suchautomatic setting of the locking brake when in gear, for examplestopping for a light, will definitely contribute to comfort. If thisfunction of automatic actuation of the locking brake is not to beoperative in general, but only at the will of the driver, then it ispossible in simple manner to activate this function by way of an AUTOswitch integrated with the electric reversing switch provided foractuation of the electric motor 1. This function may then be indicatedto the operator by a light-emitting diode or the like.

Using the electronic regulating and control means, it is of coursepossible also in simple manner to automatically release the electricallyset locking brake, for example, in the case of motor vehicles withautomatic transmission, when the engine is running, the automatictransmission 1f is in gear, and the accelerator 1a is actuated. In motorvehicles with manually actuated transmission 1f, the automatic releaseof the electrically set locking brake may for example take place whenthe engine is running, the transmission 1f is in gear, the gas pedal isactuated, and the clutch is engaged to a certain extent by correspondingactuation of the clutch pedal.

As is known, overbraking of the rear axle of a motor vehicle will inprinciple lead to an unstable condition. Using the electronic regulatingand control means, then, it is possible in simple manner, when a certainroad speed threshold is exceeded, for example one of about 20 kilometersper hour, to permit an electrical actuation of the locking brake onlywhen the driver quite deliberately operates the electric reversingswitch 1a for actuation of the electric motor 1; this means that theelectric motor 1 will automatically be reversed into the direction ofreleasing the locking brake as soon as the reversing switch is releasedonce more.

The electric motor driven actuating means for a motor vehicle lockingbrake as above described may by very simple design means be modified sothat if necessary, or at will, it may be actuated manually by means of aconventional pivoted hand brake lever, as is the case in the embodimentshown by way of example in FIG. 1.

In this arrangement, the hand brake lever 9 is pivotably articulated tothe frame of the vehicle about an axis 8 at a distance from andtransverse to the lengthwise extent of the lever 7 and transmissionelement 2, and as a rule transverse to the longitudinal axis of thevehicle as well. About the same axis 8, a substantially shorteractuating lever 10, compared to the hand brake lever 9, may also bepivoted, its free end being articulated to the motor end of thetransmission element 2, i.e. of the cable 21, in common with the lever7. The hand brake lever 9 and actuating lever 10 are not rigidlyconnected, i.e. they are in principle pivotable relative to each other.

On the hand brake lever 9, however, a follower mechanism is arranged,namely a follower 11, which loosely embraces the actuating lever 10 frombehind in its rest position (solid lines in FIG. 1) when the hand brakelever 9 is in its stand-by or rest position "a."

When the hand brake lever is put in the usual manner out of its restposition "a" for manual actuation of the locking brake, i.e. swung aboutits pivot 8, then the follower 11 forces the actuating lever 10 torotate about the pivot 8 likewise, thrusting the lever 7 in thedirection of the arrow x; the spur 6 of the lever then slips over thethread of the spindle 4, stationary because of its self-locking feature.The serrated configuration of the thread advantageously facilitates the"skipping" of the threads by the spur 6 in the direction of the arrow xin the first place, and brings it about that the spring means 13 needexert only slight radial engaging forces to ensure that the retainingforces of the transmission element 2, acting contrary to the directionof the arrow x when the locking brake is set, will be dependably takenup by the thread 5 of the spindle 4.

In FIG. 1, the positions assumed by the hand brake lever, the actuatinglever and the spur lever are indicated in dot-dashed lines and marked9', 10' and 7' respectively. When the hand brake lever has been swungfar enough to achieve the required or desired retaining force of thelocking brake, the spur lever 7', the actuating lever 10' and the cable21' retain the positions they occupy by reason of the dynamic andgeometric interlock between spur 6 and thread 5 and by reason of theself-locking design of the gear 3 and the thread etc. The hand brakelever itself may at the same time if desired--being coupled to theactuating lever 10 only by its follower 11--be "put away" again in itsrest position "a." It is easily seen that the hand brake lever 9 willtherefore remain in its rest position "a" as shown in the case of purelyelectrical actuation of the locking brake. Thus in purely electricalactuation of the locking brake, the hand brake lever will not by anymeans swing automatically, thus possibly annoying the driver. Formechanical release of the locking brake, a mechanism is provided in thehand brake lever 9, in the embodiment shown by way of example a cablemechanism 12 actuable by means of a pushbutton 13, whereby the spur 6 oflever 7 can be disengaged from the thread 5 of the spindle 4 against theforce of the spring means 13 and against the action of the frictional orlocking forces there prevailing, thus releasing the geometric anddynamic interlock between spindle 4 and lever 7, and allowing thetransmission element 2 and the actuating lever 10 and spur lever 7 toreturn into their basic position under the influence of the cable forcesacting against the direction of the arrow x.

The mechanical release of the locking brake may take place equally withhand brake lever 9 or 9' in rest position "a" or in locking position"b." With hand brake lever 9 and follower 11 in rest position, releaseof the locking brake is very rapid, abrupt as it were, since afterdisengagement of the spur 6 from the thread 5, the actuating lever canreturn from its position marked 10' to its rest position marked 10 quiteunhindered.

If instead the release of the locking brake takes place with hand brakelever 9' drawn up, i.e. in position "b," the locking brake mayalternatively be released in customary manner more slowly and well undercontrol; for in that case, the follower 11 of the hand brake lever is incontact with the disengaged actuating lever 10'.

We claim:
 1. An actuator for a motor vehicle locking brake comprising areversible electric motor, a threaded spindle driven by the electricmotor, a spur lever connected to one end of a force-transmitting memberleading to a brake, and a spur on the spur lever for directly engagingthe thread of the spindle, the drive connection between the electricmotor and the spur lever including a self-locking connection.
 2. Anactuator according to claim 1, including an electric reversing switchfor switching the electric motor on and off and at the same timeselecting its direction of rotation as required to set or release thelocking brake.
 3. An actuator according to claim 1, including electronicregulating and control means responsive to at least one operatingparameter of the motor vehicle or of the electric motor for functionalmonitoring and/or control of the locking brake.
 4. An actuator accordingto claim 3 wherein the electronic regulating and control means includesmeans for automatically setting the locking brake when the motor vehicleis stopped on an incline.
 5. An actuator according to claim 3 whereinthe electronic regulating and control means includes means forautomatically setting the locking brake when the vehicle is stationary.6. An actuator according to claim 4 or claim 5 wherein the vehicle hasan automatic transmission and wherein the electronic regulating andcontrol means includes means for automatic release of the locking brakeas soon as the automatic transmission is put in gear and the acceleratoractuated with the engine running.
 7. An actuator according to claim 4 orclaim 5 wherein the vehicle has a manual transmission and wherein theelectronic regulating and control means includes means for automaticrelease of the locking brake as soon as the manual transmission is putin gear, the gas pedal is actuated, and the clutch is engaged to acertain extent by appropriate actuation of the clutch pedal with theengine running.
 8. An actuator according to claim 3 wherein theelectronic regulating and control means includes means for automaticrelease of the locking brake when a preassigned road speed is exceededand the electric reversing switch is not held in a position causing thelocking brake to be set.
 9. An actuator according to claim 1, includinga handbrake lever pivotable about an axis spaced from and transverse tothe lengthwise extent of the spur lever and of the force-transmittingmember, a pivotably supported actuating lever substantially shorter thanthe handbrake lever, connected together with the spur lever to the oneend of the force-transmitting member, a follower mechanism on thehandbrake lever loosely embracing the actuating lever and acting in onedirection only, whereby swinging motion of the handbrake lever only inthe direction to set the locking brake can be transmitted to theactuating lever.
 10. An actuator according to claim 9, including arelease mechanism arranged in the handbrake lever for disengaging thespur from the thread of the spindle.